The invention relates to energization systems for electric fences, and more particularly to a coupled series and parallel resonant circuit for an electric fence apparatus, which contains, in addition to its parallel inductance, its smaller series inductance, the parallel and series (fence) capacitances respectively, and the ohmic circuit resistances, an automatic switching element or device through which the parallel capacitance is charged from a voltage source to an operating voltage (U.sub.1) and is wired to the parallel inductance. Transients, occurring via the series inductance first upon the activation of the switching element, charge the series capacitance or fence to a transient voltage (U.sub.2) which is appreciably higher than the supply or operating voltage (U.sub.1).
Coupled series and parallel resonant circuits of the kind described above are known in electric fence apparatuses; the parallel capacitance comprises a charging capacitor which is connected in parallel with the primary side of a pulse transformer. The series capacitor is the fence capacitance that is connected in parallel with the secondary side of the pulse transformer; the ohmic circuit resistances are the unavoidable ohmic resistances of the windings and the insulation resistance of the fence wire. The parallel inductance is constituted of the principal inductance of the pulse transformer, and the series inductance is constituted of the leakage inductance of the pulse transformer. Normally, the leakage inductance of the pulse transformer is considerably smaller than the principal inductance (such as about 10%), and the capacitance of the fence to ground is likewise considerably smaller than that of the charging capacitor.
It is also known in such circuits to use a thyristor or transistor as the switching device or element. When the switching element in the known arrangements is closed, a transient current will first flow via the series inductance and the series capacitance, with the transient voltage at the series capacitance increasing up to twice the voltage at the parallel capacitance, depending on the selection of the switching elements. Due to the series connection of the parallel capacitance and the series capacitance, the total or overall series capacitance is small, as is also the series inductance. Therefore, the frequency of the transients is relatively great, and the pulse width is very narrow.
In addition, the transients are subject to severe attenuation. Therefore, what practically occurs is a one-time overswing, going over into a cosine function as the principal oscillation. This principal oscillation is essentially determined by the parallel capacitance and the parallel inductance, with the operating voltage (U.sub.1) representing the peak voltage of the cosine function.
The effect of an electric fence apparatus on an animal depend a greatly on the pulse data. The pulse voltage should be as high as possible and also the pulse width, so that the voltage-time area is great; the effect is particularly intense if the pulses are already wide at their peaks. But in the prior arrangement described above, the shock effect at the fence is essentially determined by the cosine function and the narrow overswing contributes virtually nothing to the shock effect.
Another deficiency of the above-described arrangement in electric fence apparatuses is its high loss of electric energy. The switching element commonly used in the above described known arrangement is a thyristor which allows the positive current half-wave to pass while blocking currents attempting to flow in a reverse direction. During the positive current half-wave, the charging capacitor or the parallel capacitance is charged to a small reverse polarity which is only a fraction of the operating voltage (U.sub.1), because of the attenuation. For this negative or reverse voltage, the charging circuit of prior devices (not described here in detail) is connected in the forward or flow direction. This charging capacitor is thus seen to discharge down to zero and then to be recharged to its operating voltage (U.sub.1), whereupon the cycle continually repeats.
Depending on the size of the fence capacitance, the maximum energy stored in the fence capacitor (with the maximum fence voltage) is only a fraction of the energy in the charging capacitor, so that the differences or differential energy is lost. In electric fence apparatuses of usual design and with usual fence lengths, two to three times the amount of energy applied to the fence must be fed to the charging capacitor. These energy losses are particularly disadvantageous in apparatuses fed by dry cells, the energy of which is very expensive.